The background of the invention relates to problems with the prior art in context of injection of water into subterranean hydrocarbon reservoirs in order to increase the degree of recovery from such reservoirs, so-called secondary recovery. Water injection, or water flooding, constitutes the most common method of increasing the degree of recovery of crude oil from a reservoir. During such water injection, the is object is to maintain the pressure in the reservoir and simultaneously force crude oil out of the reservoir via at least one production well positioned downstream of a water-flood front.
A further development of such a secondary recovery method is usually referred to as tertiary recovery. Such tertiary recovery may comprise, among other things, admixing of one or more chemicals, thereby arranging the injection water with one or more advantageous properties before the injection water flows through the injection well and further out into a subterranean oil reservoir. In this context, it is common, for example, to admix surface-active agents, so-called tensides (“surfactants”), into the injection water, thereby improving the washing properties of the water in the reservoir. Such surface-active agents reduce the surface tension of the crude oil, whereby the crude oil becomes more mobile and easier to wash out of the reservoir by means of an injection water front. Different, known types of surface-active agents are available and are used in this context.